Hydraulic brake booster and control valve therefor

Abstract

A hydraulic brake booster defines a pressure chamber (24) and includes a control valve (26). A sleeve (40) on the control valve includes a spacer (58) and the control valve includes an annular member (60). The spacer is engageable with a booster housing (14) to limit movement of the sleeve and the annular member is engageable with an accumulator valve assembly (32) during a failure mode to provide a safety power assist. The spacer is also maintained in spaced relation to the accumulator valve assembly.

I claim: 
     
       1. In a hydraulic brake booster, a housing having an inlet and substantially defining a pressure chamber, a control valve movably disposed within the housing and being operable to communicate fluid pressure from the inlet to the pressure chamber, an accumulator normally storing fluid pressure and communicating with the pressure chamber when the control valve is operable and the fluid pressure within the pressure chamber is below a predetermined value, valve means cooperating with the accumulator to normally close communication between the accumulator and the pressure chamber, a sleeve member carried by the control valve and being movable relative to the control valve to close communication between the inlet and the pressure chamber when the fluid pressure in the latter is below the predetermined value, and an annular member engageable with the valve means to open communication between the accumulator and the pressure chamber, characterized by the sleeve member including a portion which is engageable with the housing to limit movement of the sleeve member when the control valve is operable and the annular member is movable with the control valve when the portion is engageable with the housing to engage the annular member with the valve means. 
     
     
       2. The hydraulic brake booster of claim 1 characterized by the portion of the sleeve member comprising a separate part which is maintained in engagement with the sleeve member by a resilient member. 
     
     
       3. The hydraulic brake booster of claim 1 characterized by a resilient member extending between the annular member and the sleeve member portion. 
     
     
       4. The hydraulic brake booster of claim 1 characterized by the annular member including a plurality of openings and the portion of the sleeve member extends through the openings to face the housing. 
     
     
       5. The hydraulic brake booster of claim 1 characterized by the control valve defining a shoulder and the annular member is normally biased into engagement with the shoulder. 
     
     
       6. The hydraulic brake booster of claim 1 characterized by the control valve and annular member being movable relative to the sleeve member to engage the annular member with the valve means and the sleeve member continues to close communication between the inlet and the pressure chamber. 
     
     
       7. The hydraulic brake booster of claim 1 characterized by the portion being engageable with the housing at a predetermined maximum pressure level within the pressure chamber. 
     
     
       8. In a hydraulic brake booster having a housing substantially defining a pressure chamber and movably supporting a control valve, the control valve being operable to move relative to the housing to communicate fluid pressure to the pressure chamber, the control valve also including means responsive to the fluid pressure within the pressure chamber to limit movement of the control valve when the fluid pressure within the pressure chamber is above a first predetermined amount, a sleeve cooperating with the control valve to close communication with the pressure chamber when the control valve is operable and the fluid pressure within the pressure chamber is below a second predetermined amount, a spacer cooperating with the sleeve and engageable with the housing to limit movement of the sleeve, and an accumulator selectively communicating with the pressure chamber via a dump valve, characterized by the spacer being engageable with the housing when the fluid pressure within the pressure chamber is above the first predetermined amount and the spacer being at all times remote from the dump valve, and the control valve including a portion movable therewith to engage the dump valve to open the accumulator to the pressure chamber when the fluid pressure therein is below the second predetermined amount. 
     
     
       9. The hydraulic brake booster of claim 8 in which said spacer is engageable with the housing at substantially the same time that said means is responsive to the fluid pressure with the fluid pressure chamber to limit movement of said control valve. 
     
     
       10. A hydraulic brake booster comprising a housing substantially defining a pressure chamber, a control valve movably disposed within said housing and being operable to communicate fluid pressure to said pressure chamber, means responsive to the fluid pressure within said pressure chamber to limit movement of said control valve when the latter is operable, a sleeve member carried by said control valve and being movable relative to said control valve from a first position opening communication to said pressure chamber to a second position closing communication to said pressure chamber, an accumulator normally storing pressurized fluid and selectively communicating with said pressure chamber via a dump valve, and said control valve including a portion cooperating with said dump valve to open said accumulator to said pressure chamber when said sleeve member is in the second position and said control valve is movable relative to said sleeve member, said sleeve member including a spacer engageable with said housing when said sleeve member is in the second position. 
     
     
       11. The hydraulic brake booster of claim 10 in which a resilient member extends between and is engageable with said control valve portion and said sleeve member portion.